To determine whether myocardial stunning differs among dogs, pigs and baboons, and is reproducible within species, we examined 9 conscious dogs, 12 minipigs, and 6 baboons chronically instrumented with a left circumflex coronary occluder, dimension crystals, left ventricular pressure gauge and aortic and left atrial catheters. During 10 min coronary artery (CA) occlusion (O), systolic wall thickening in the ischemic zone fell similarly in dogs (-108q5.6%), pigs (-102q1.8%) and baboons (-107q5.7%), but blood flow fell more, p<0.05, in the subepicardium in pigs (0.07q0.01 ml/min/g) and baboons (0.07q0.02 ml/min/g) than in dogs (0.18q0.03 ml/min/g). At 1 hr after CA reperfusion (R), wall thickening was reduced more (p<0.05) in dogs (-40q4.2%) than pigs (-22q2.1%) and baboons (-4q2.4%). wall thickening returned to baseline levels later (68q9 min) during CAR in baboons, pigs (4.3q0.5 hr), and in dogs (12.0q2.4 hr). In 5 dogs and 5 pigs, 3 separate 10 min CAO, each 2 days apart, were also examined. In dogs, effects during CAO were similar but reductions in wall thickening after CAR were significantly less following the second (-26q4.2%) or third (-30q3.2%) CAO, compared to the first CAO (-47q4.9%). In contrast, repetitive CAO did not induce differences in recovery of wall thickening in pigs. In 4 dogs where increases in myocardial metabolism were minimized by pretreatment with ganglionic and a-adrenergic receptor blockades, depression of wall thickening at 1 hr CAR was similar (-52q12.2%) to that observed in dogs when heart rate rose in the intact state. Furthermore, the recovery of wall thickening following CAR was also improved after the third as compared with the first CAO. These results indicate that myocardial stunning is less severe in conscious pigs and baboons, as compared with conscious dogs, despite more intense transmural ischemia. The conscious dogs demonstrated a "preconditioning-like effect," with serial brief CAO, which was not exhibited in conscious pigs.